rust-neckbeard

Rust Neckbeard Style

Canonical reference: style/style.md and docs/src/style/rust.mdx. Enclave crates (apps/cloud/apps/enclave/) are decent (not perfect) examples.

File Header

Every source file opens with the copyright line, then a blank line, then module docs:

// Copyright (c) 2026 Dedalus Labs, Inc. All rights reserved.

//! Module purpose in one sentence.

The copyright line uses // (not //!) because it is not Rustdoc output.

Algorithmic Preamble

For files that implement a non-trivial algorithm or protocol, add a numbered step summary inside the module doc. The reader should be able to reconstruct the high-level flow without reading function bodies.

Not every file needs this -- only files whose control flow would confuse a reader six months from now. Wire types and thin delegation layers skip it.

Hard Limits

• Functions: 70 lines
• Files: 500 lines (excluding #[cfg(test)] module)
• Nesting: 3 levels
• Arguments: 5 (excluding &self/&mut self)
• PRs: 200 changed LOC

If a function exceeds 70 lines, extract helpers. If a function exceeds 5 args, bundle related params into a config/context struct.

Implicit Last Expression Is Idiomatic

Rust's implicit last expression is the language's idiom for return values. Clippy's default let_and_return lint warns against let x = expr; x. Do not fight the linter.

// GOOD: idiomatic Rust
fn socket_path(&self, id: &WorkspaceId) -> PathBuf {
    self.socket_dir().join(format!("{id}.sock"))
}

// BAD: triggers clippy::let_and_return
fn socket_path(&self, id: &WorkspaceId) -> PathBuf {
    let path = self.socket_dir().join(format!("{id}.sock"));
    path
}

When a return expression is genuinely complex (multi-line match, long chain with ?), a named binding improves readability. Use judgment, not a blanket rule. If the binding name is just result, you're not adding clarity.

#[must_use] on Pure Functions

Annotate every public or pub(crate) function whose return value would be a bug to ignore. This includes: